Wellhead piping or other piping systems are at risk for erosion from particulate-laden fluid streams passing therethrough, often at very high pressures. The particulate-laden fluid is often environmentally and otherwise hazardous. Thus, breaches or failures in a fitting in said piping can be catastrophic.
In particular, sand, in a stream of fluid such as gas, can cause significant erosion to the components at areas of high turbulence such as changes in flow direction. Right angle or 90 degree elbows or T-junctions and bends are particularly vulnerable areas in an environment having high pressure ratings and where the fluid itself is hazardous, being, among other things, both toxic and flammable.
Many have attempted to resolve the problem by attempting to prevent corrosion of the fittings. Designs for fittings have been altered or materials selected which are less easily corroded, however, Applicant believes that the problem remains significant, particularly when dealing with fluids containing hazardous fluids, such as H2S.
Some operators have altered the design by installed a tee fitting at an elbow, one branch of the tee being blocked off at the turn, ideally to collect sand to act as a buffer or pad to minimize erosion of the structural aspects of the elbow behind the sand pad. Unfortunately, the flow dynamics are complex and the sand may not reliably collect at the blocked branch, or wear occurs adjacent thereto and elsewhere.
Others have used low carbon steel pipes made of steel containing more chromium, or ceramic coated fittings, however the expense to replace fittings with a higher cost component is typically prohibitive and washing out may still occur.
Further, some have bored an elbow fitting into a block of steel to provide reinforcement to the elbow and delay failure due to washing out of the elbow.
It is known to use a variety of sensors or systems to detect corrosion and wear in components. U.S. Pat. No. 5,740,861 to Williams teaches a detector which includes a replaceable erosion block which is inserted into a fitting. The erosion block comprises a passage and bores intercepting the passage. A probe, having an erodable contact, is inserted into the bore of the block and is in contact with the passage. When a breach of the fitting occurs, the probe senses an increase of pressure in the bore which is detected via a pressure transducer at a monitoring station. A breach in the bore does not result in loss of pressure as pressure containment is maintained by the erosion block. Applicant believes that given the expense to manufacture and maintain such a system, only a single probe would be positioned at a point where the likelihood of wear is predicted, however, the remainder of the fitting is essentially unmonitored. Should a failure occur at a position other than predicted, the fitting is at risk of a catastrophic breach, without warning.
U.S. Pat. No. 4,779,453 to Hopenfield discloses a method of monitoring thinning in piping wherein a plurality of holes having different depths are bored in the outer surface of a pipe at selected locations having greatest risk of erosion or corrosion. Tracer materials are inserted into the holes and are plugged and welded. Monitoring equipment is positioned downstream from the holes and the fluid flow through the piping is monitored for the presence of the tracer material which would only be present as a result of a breach. Unique tracers can be positioned in holes having different depths or at different locations of turbulence in the pipe so that the degree and/or location of thinning can be readily determined. Use of holes which extend to the outer surface of the pipe, regardless of the strength of the plug or weld, may place the environment around the pipe at risk should a breach occur.
Others, such as U.S. Pat. No. 4,655,077 to Purvis et al have attempted to use sensors, such as conductive loops, embedded throughout the component to signal wear. As wear reaches each level of conductive loop positioned therein the sensor circuit is interrupted and thus detected. The continuity status of each loop is evaluated periodically, with an electrical closed circuit condition indicating structural integrity at that particular loop location, and an electrical open circuit condition indicating such a wear condition.
Clearly, what is required is means for detecting the integrity of a fitting and to provide some warning of imminent failure of the fitting that is simple, inexpensive, and reliable.